diameter

[teng125]

The rod shall be replaced by a tube (wall thickness s =
da=12).if da is the outer diameter,then the inner diameter is it di=da-da/12 ??

[Meson]

Be careful, recommended to draw the cross-section when evaluating the inner diameter for a clearer view.

d_{i}=d_{a}-2(\frac{d_{a}}{12})=\frac{5}{6}d_{a}